NAME¶

SDL_CreateRWLock - Create a new read/write lock.

SYNOPSIS¶

#include "SDL3/SDL.h"

SDL_RWLock* SDL_CreateRWLock(void);

DESCRIPTION¶

A read/write lock is useful for situations where you have multiple threads trying to access a resource that is rarely updated. All threads requesting a read-only lock will be allowed to run in parallel; if a thread requests a write lock, it will be provided exclusive access. This makes it safe for multiple threads to use a resource at the same time if they promise not to change it, and when it has to be changed, the rwlock will serve as a gateway to make sure those changes can be made safely.

In the right situation, a rwlock can be more efficient than a mutex, which only lets a single thread proceed at a time, even if it won't be modifying the data.

All newly-created read/write locks begin in the _unlocked_ state.

Calls to SDL_LockRWLockForReading () and

SDL_LockRWLockForWriting
will not return while the rwlock is locked _for writing_ by another thread. See

SDL_TryLockRWLockForReading () and

SDL_TryLockRWLockForWriting () to attempt to lock without blocking.

SDL read/write locks are only recursive for read-only locks! They are not guaranteed to be fair, or provide access in a FIFO manner! They are not guaranteed to favor writers. You may not lock a rwlock for both read-only and write access at the same time from the same thread (so you can't promote your read-only lock to a write lock without unlocking first).

RETURN VALUE¶

Returns the initialized and unlocked read/write lock or NULL on failure; call SDL_GetError () for more information.

AVAILABILITY¶

This function is available since SDL 3.0.0.

SEE ALSO¶

SDL_DestroyRWLock(3), SDL_LockRWLockForReading(3), SDL_LockRWLockForWriting(3), SDL_TryLockRWLockForReading(3), SDL_TryLockRWLockForWriting(3), SDL_UnlockRWLock(3)